OF LOWER GREENSAXD PLANTS. :J9."> 



APPENDIX. 



The following species are not included in the body of the 

 descriptive text because their age is rather doubtful. Though 

 they were found in the " Pott on Sands," which are of Lower 

 Greensand age, it is generally held that Potton fossils of the 

 colour and texture of these (a rich red-brown liraonite) are 

 derived from the Wealden. 



They are included in the present volume not only to complete 

 the account of the fossils found in the Lower Greensand, but 

 also because they afford new evidence regarding the hitherto 

 neglected anatomy of Cycadeoidea as distinct from Bemiettites 

 (see p. 23). 



Genus CYCADEOIDEA, Buckland. 



[Proc. Geol. Soc., vol. 1, no. 8, 1828, pp. 80, 81 ; and Trans. 

 Geol. Soc., ser. 2, vol. 2, 1828, pp. 395-401.] 



Diagnosis. Genus founded on vegetative trunks, which are 

 of uncertain height, some conical or ovoid, some cylindrical, 

 covered b) r closely arranged leaf-bases, generally rhombic in 

 shape, which may or may not be transversely elongated. In 

 its internal anatomy the trunk shows two or more (up to eight 

 are recorded) zones of secondary wood, the zones composed of 

 distinct series of tracheids each more or less regularly arranged 

 in radial sequence. Pith very large, with gum-canals, but no 

 vascular strands. 



In the above diagnosis, which is provisional until more is 

 known of the fossils, the clear distinction between Cycadeoidea 

 and Bennettites is presented for the first time. 



Much confusion has existed on the subject of the nomen- 

 clature of the Cy cad-like fossil trunks since 1823, when 

 Buckland founded the genus Cycadtoidca, followed almost at 

 once by Brongniart's genus Mantellia. Many other so-called 

 genera have since been founded, e. g. Yatesia, Can*., ClatJiraria, 

 Schinip., etc., but these are generally recogni/ed as being based 

 more on differences in the preservation than in the actual 



